In recent years, improvements in video processing techniques have made it possible to transmit high-quality videos, for example, high-definition television. Here, digital video signals in accordance with high-definition television broadcasting are transmitted to individual homes through wireless or wired transmission means. However, since the transmission capacity of each transmission means is limited, digital video signals having a large amount of data are often compressed and then transmitted. For compression techniques, conforming to MPEG (Moving Picture Experts Group) are known.
However, when a compressed digital video, which has been transmitted, is received and decompressed at a receiving side, sometimes the video has a problem in quality. Accordingly, in order to check such video quality, checking techniques have been developed (Refer to Japanese Unexamined Patent Application Publication No. 10-285594).
In the known technique described above, a video and its analysis result are displayed separately. If a video and its analysis result are multiplexed and displayed on one screen, the observer can grasp the characteristic of the video at a glance while viewing the video which is being played back in real time. However, when analyzing a transmitted digital video signal in real time, there is a problem in that the signals cannot be multiplexed in real time due to the time difference between the decoded video signals and analysis results, because the digital video signal is being transmitted while the analysis is performed. In order to solve this problem, the multiplexing of the signals by separately providing a memory for buffering the decompressed digital video signal and the reading of the memory in synchronization with the end of the analysis can be considered. However, this is not a realistic solution since a vast capacity of memory is required.
Also, there are demands that when an error occurs with a digital video signal, the error should be detected within a short time.